This invention relates to a color picture tube having an electron gun with a plurality of cathodes and apertured electrodes therein that produces three electron beams, and, more particularly, to an inline electron gun wherein at least one of the electrodes includes optimized attachment means for securing the electrode to a plurality of electrically insulative support rods so as to minimize the bending moment of the electrode, and for reducing the spacing variations between adjacent electrodes while maintaining the aperture alignment therebetween.
The electrode members of an inline electron gun assembly, such as that shown in FIG. 1, are serially arranged to accelerate and focus a plurality of electron beams along spaced, coplanar electron beam paths. The electrode members of the gun assembly are mechanically secured by attachment means and studs to at least a pair of insulative support rods which extend, longitudinally, along the beam paths. Each of the electrode members commonly has several spatially-related apertures formed therein to accommodate the respective electron beams generated within the electron gun. It is important that these several apertures be accurately located and aligned relative to the related apertures in adjacent electrode members, and to the respective electron generating surfaces. During the fabrication of the electron gun assembly, the attachment means and studs of the various electrode members are embedded into the temporarily heat-softened insulative support rods, at which time the support rods on opposed sides of the gun assembly are pressured inwardly toward the electrode members to force the attachment mean and studs into the support rods. The compressive pressure tends to exert a distorting force upon the electrode members of the electron gun assembly.
Co-pending U.S. Patent Application Ser. No. 325,840, filed on Mar. 20, 1989 by J. R. Hale and G. J. McCauley, entitled, STRENGTHENING MEANS FOR A SIDEWALL OF A CUP-SHAPED MEMBER FOR AN ELECTRON GUN OF A CRT discloses a structure for strengthening a deep-drawn cup-shaped electrode by forming coined, stud-securing areas in the sidewall of the electrode. It also is known in the art, for example in U.S. Pat. No. 4,049,991, issued on Sept. 20, 1977 to Collins, to strengthen a planar electrode member by forming strengthening bends and rib embossments in the planar surface of the member.
With recent utilization of large screen inline color CRT's for both CAD/CAM and entertainment applications, a reduced electron beam spot size over the entire screen is necessary for the high resolution requirements of such applications. Several electron guns which meet these high resolution requirements are described in the literature, for example, a six element (electrode) electron gun is described in an article entitled, DYNAMIC ASTIGMATISM CONTROL QUADRA POTENTIAL FOCUS GUN FOR 21-IN. FLAT SQUARE COLOR DISPLAY TUBE, by T. Katsuma et al. in SID Digest, 136 (1988). U.S. Pat. No. 4,877,998, issued on Oct. 31, 1988, also describes a six element electron gun having improved performance. Each of the above-mentioned electron guns requires a large number of closely spaced attachment claws embedded into the longitudinally extending insulative support rods of the electron gun such as those shown for the electron gun assembly of FIG. 1. A major drawback of such an electron gun structure is that/in the low voltage end of the electron gun assembly, i.e., in the vicinity of the G1 through G4 electrodes, the attachment claws are generally transversely disposed within the insulative support rods which are vulnerable to cracking due to stresses during tube processing (thermal stress during gun fabrication and high voltage stress during high voltage processing). One expedient, the formation of conventional vertically oriented attachment claws, attempts to minimize these stresses by orienting the claws along the longitudinal axes of the rods; however, the conventional vertical claws also include transversely disposed horizontal support tabs, as shown in FIG. 2, which tend to negate the advantage of the vertical portion of the claws (shown in FIG. 3) because the horizontal tabs also are embedded into the support rods. Another drawback of the vertically oriented attachment claws is that the offset of the claws with respect to the plane of the grid electrode introduces a bending moment during the fabrication operation, which causes spacing variations between the grid electrode with the vertical claws and adjacent electrodes, and contributes to aperture misalignment caused by movement of the subject electrode. Thus, a need exists for an improved attachment claw configuration that decreases the vulnerability to cracking of the support rods by eliminating the transversely disposed horizontal tabs while minimizing the bending moment of the grid electrode caused by the offset of the conventional vertical claw.